Processes for the preparation of isocyanates

Inactive Publication Date: 2007-11-22
BAYER MATERIALSCIENCE AG
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  • Abstract
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  • Application Information

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Benefits of technology

[0007] One object of the present invention includes providing a process for the preparation of isocyanates which can include at least partial recycling of the hydrogen chloride obtained during the preparation of the isocyana

Problems solved by technology

However, the amounts of hydrogen chloride produced as a by-product cannot always be marketed or employed for other syntheses in their entirety.
Disposal of hydrogen chloride, e.g., by neutralization with alkali, can be unattractive for economic and ecological reasons.
A disadvantage of the known heterogeneously catalysed oxidation of hydrogen chloride (Deacon process) is the incomplete conversion (up to 90%) at the reaction temperature required for the reaction with the known catalysts, which is conventionally in the range

Method used

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  • Processes for the preparation of isocyanates
  • Processes for the preparation of isocyanates

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examples

[0071] A process according to an embodiment of the invention is explained in more detail with reference to FIG. 1. FIG. 1 is a representative flowchart depicting a process according to the invention for the preparation of TDI.

[0072] In a first stage 1 of the preparation of isocyanates, chlorine 11 is reacted with carbon monoxide 10 to give phosgene 13. In the following stage 2, phosgene 13 from stage 1 is reacted with an amine 14 (in this case toluenediamine) to give a mixture 15 of isocyanate (toluene-diisocyanate, TDI) and hydrogen chloride, the isocyanate 16 is separated off (in stage 3) and utilized. The HCl gas 17 is reacted with oxygen 18 in the HCl oxidation process 4.

[0073] For this e.g., a UV-transparent reaction tube can be used, this being charged with HCl and O2 in the stoichiometric ratio of 4:1. The reaction mixture is irradiated in the reaction tube with short wavelength (<250 nm), coherent UV light with the aid of a pulsed excimer laser. The temperature of the reac...

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Abstract

Processes are described which comprise: (a) reacting chlorine with carbon monoxide to form phosgene; (b) reacting the phosgene with at least one organic amine to form at least one isocyanate and hydrogen chloride; (c) separating the hydrogen chloride; (d) oxidizing the hydrogen chloride with oxygen in a gas phase to form additional chlorine; and (e) recycling at least a portion of the additional chlorine to the reaction of the chlorine and the carbon monoxide; wherein the oxidation of the hydrogen chloride is initiated via a high energy source which may be selected from electron-exciting radiation, ionizing radiation, a gas discharge, a plasma, and combinations thereof.

Description

BACKGROUND OF THE INVENTION [0001] Chlorine is very often employed as an oxidizing agent in the production chain for the preparation of many organic compounds and for the preparation of raw materials for the production of polymers. Hydrogen chloride is often formed as a by-product in such reactions. For example, chlorine is employed in the preparation of isocyanates and hydrogen chloride is formed as a by-product. The hydrogen chloride can be utilized further, e.g., by marketing of an aqueous solution (hydrochloric acid) or by use in syntheses of other chemical products. [0002] However, the amounts of hydrogen chloride produced as a by-product cannot always be marketed or employed for other syntheses in their entirety. Furthermore, hydrogen chloride can normally be employed for synthetic purposes only if it has been appropriately purified beforehand. The marketing and sale of by-product hydrogen chloride is usually economical only if the hydrogen chloride or the hydrochloric acid do...

Claims

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Application Information

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IPC IPC(8): C01B7/00C07C263/10C01B32/40C01B32/80
CPCC01B7/035C01B7/04C01B7/0706C07C263/10C07C263/20C07C265/14
Inventor WEBER, RAINERKINTRUP, JURGENBULAN, ANDREASSOPPE, ALFREDWEISS, MARTIN
Owner BAYER MATERIALSCIENCE AG
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